1. Field of the Invention
This invention relates to a plasma display panel, and more particularly to a plasma display panel that is capable of minimizing a brightness difference.
2. Description of the Related Art
Recently, a plasma display panel (PDP) feasible to a manufacturing of a large-dimension panel has been highlighted as a flat panel display device. The POP typically includes a three-electrode, alternating current (AC) surface discharge PDP that has three electrodes and is driven with an AC voltage as shown in FIG. 1.
Referring to FIG. 1, a discharge cell of the three-electrode, AC surface discharge PDP includes a scanning/sustaining electrode 12Y and a common sustaining electrode 12Z formed on an upper substrate 10, and an address electrode 20X formed on a lower substrate 18. On the upper substrate 10 in which the scanning/sustaining electrode 12Y is formed in parallel to the common sustaining electrode 12Z, an upper dielectric layer 14 and a protective film 16 are disposed. Wall charges generated upon plasma discharge are accumulated in the upper dielectric layer 14. The protective film 16 prevents a damage of the upper dielectric layer 14 caused by the sputtering generated during the plasma discharge and improves the emission efficiency of secondary electrons. This protective film 16 is usually made from MgO. A lower dielectric layer 22 and barrier ribs 24 are formed on the lower substrate 18 provided with the address electrode 20X, and a fluorescent material 26 is coated on the surfaces of the lower dielectric layer 22 and the barrier ribs 24. The address electrode 20X is formed in a direction crossing the scanning/sustaining electrode 12Y and the common sustaining electrode 12Z. The barrier ribs 24 is formed in parallel to the address electrode 20X to prevent an ultraviolet ray and a visible light generated by the discharge from being leaked to the adjacent discharge cells. The fluorescent material 26 is excited by an ultraviolet ray generated upon plasma discharge to produce a red, green or blue color visible light ray. An active gas for a gas discharge is injected into a discharge space defined between the upper/lower substrate and the barrier rib.
As shown in FIG. 2, such a discharge cell is arranged in a matrix type. In FIG. 2, the discharge cell 1 is provided at each intersection among scanning/sustaining electrode lines Y1 to Ym, common sustaining electrode lines Z1 to Zm and address electrode lines X1 to Xn. The scanning/sustaining electrode lines Y1 to Ym are sequentially driven while the common sustaining electrode lines Z1 to Zm are commonly driven. The address electrode lines X1 to Xn are driven with being divided into odd-numbered lines and even-numbered lines.
Such a three-electrode, AC surface discharge PDP is driven with being separated into a number of sub-fields. In each sub-field interval, a light emission having a frequency proportional to a weighting value of a video data is conducted to provide a gray scale display. For instance, if a 8-bit video data is used to display a picture of 256 gray scales, then one frame display interval (e.g., 1/60 second=16.7 msec) in each discharge cell 1 is divided into 8 sub-fields SF1 to SF8. Each sub-field is again divided into a reset interval, an address interval and a sustaining interval. A weighting value at a ratio of 1:2:4:8: . . . :128 is given in the sustaining interval. Herein, the reset interval is a period for initializing the discharge cell; the address interval is a period for generating a selective address discharge in accordance with a logical value of a video data; and the sustaining interval is a period for sustaining the discharge in a discharge cell in which the address discharge has been generated. The reset interval and the address interval are equally assigned in each sub-field interval.
The scanning/sustaining electrode lines Y and the common sustaining electrode lines Z of the plasma display panel receive a driving waveform via a pad portion 30 shown in FIG. 3. Referring to FIG. 3, the pad portion 30 includes pads 31 for receiving a driving waveform from a driving waveform supply, and connecting parts 32 for applying the driving waveform inputted to the pads 31 to the scanning/sustaining electrode lines Y or the common sustaining electrode lines Z. Each pad 31 is connected to a connector 34 of the driving waveform supply as shown in FIG. 4. The driving waveform supply applies the driving waveform inputted to the scanning/sustaining electrode lines Y or the common sustaining electrode lines Z to the connectors 34. The driving waveform inputted to the connectors 34 is applied, via the pads 31 and the connecting parts 32, to the scanning/sustaining electrode lines Y or the common sustaining electrode lines Z. In this case, a longitudinal width of each connector 34 is formed to be narrower than a width of an effective display part in which a picture is to be displayed in compliance with a trend toward a slim-type PDP. Thus, a width of the pad 31 set in correspondence with a longitudinal width of the connector 34 also is formed narrowly. Accordingly, a length of a connecting part 32 provided between the pads 31 and the electrodes Y and Z formed at the periphery of the effective display part becomes longer than that of a connecting part 32 provided between the pads 31 and the electrodes Y and Z formed at the center portion of the effective display part. More specifically, a length sum L1+L2 of a pad 31 and a connecting part 32 for supplying a driving waveform to the electrodes Y and Z formed at the center portion of the effective display part is different from a length sum L3+L4 of a pad 31 and a connecting part 32 for supplying a driving waveform to the electrodes Y and Z formed at the periphery of the effective display part. If the lengths of the pads 31 and the connecting parts 32 provided at the pad portion 30 are different depending on their position, then a voltage applied from the pad portion 30 to the electrodes Y and Z becomes different. In other words, the electrodes Y and Z receiving a driving waveform via L3 and L4 is supplied with a smaller voltage than the electrodes Y and Z receiving a driving waveform via L1 and L2 due to a voltage drop. More specifically, the electrodes Y and Z formed at the periphery of the effective display part generates a voltage drop because they receive a driving waveform via the long connecting part L3. Thus, a brightness difference is generated between the periphery and the center of the effective display part. Also, since the conventional pad portion 30 has a large angle at a portion in which the electrodes Y and Z formed at the periphery of the effective display part are connected to the connecting part 32, a breakage may be generated in the course of a electrode fabricating process of the pad portion 30. Furthermore, the conventional pad portion 30 has a problem in that, since the conventional pad portion 30 also has a large angle at a portion in which the connecting part 32 and the pad 31 formed at the periphery of the pad portion 30 are connected to each other also, a breakage is generated in the course of its electrode fabricating to cause a product badness or deteriorate the productivity.
Meanwhile, the pad portion may be arranged in correspondence with the periphery of the effective display part as shown in FIG. 5 in consideration of a location of the connector or the circuit arrangement, etc. Referring to FIG. 5, a pad portion 38 is arranged to correspond to a first periphery 40 of the effective display part. Each pad 36 is connected to each connector 44. A driving waveform inputted from the connector 44 is applied, via a connecting part 34, to the electrodes Y and Z provided within the effective display part. If the pad portion 38 is formed at the first periphery 40 of the effective display part, then a length sum L7+L8 of the pad 36 and the connecting part 34 for applying a driving waveform to the electrodes Y and Z formed at the first periphery 40 becomes different from a length sum LS+L6 of the pad 36 and the connecting part 34 for applying a driving waveform to the electrodes Y and Z formed at a second periphery 42. Thus, a voltage supplied from the pad portion 38 to the electrodes Y and Z formed at the first periphery 40 becomes a voltage supplied from the pad portion 38 to the electrodes Y and Z formed at the second periphery 42. In other words, the electrodes Y and Z receiving a driving waveform via L5 and L6 is supplied with a smaller voltage than the electrodes Y and Z receiving a driving waveform via L7 and L8 due to a voltage drop. Accordingly, a brightness difference is generated between the first periphery 40 and the second periphery 42 of the effective display part. Furthermore, the conventional pad portion 38 has a problem in that, since the connecting part 32 connected from the second periphery 42 to the pad 38 has a large angle, a breakage is generated in the course of a manufacturing and installation process of the pad portion 38 to cause a product badness or deteriorate the productivity. The above-mentioned problems also may be generated at a pad portion (not shown) for applying a driving waveform to the address electrode lines X.
Accordingly, it is an object of the present invention to provide a plasma display panel (PDP) that is capable of minimizing a difference, that is, a voltage drop applied to an effective display part to diminution the brightness difference.
A Further object of the present invention is to provide a PDP wherein an angle between an effective display part and a connecting part and an angle between a connecting part and a pad are slowly formed so as to minimize a breakage that may be generated in the course of a electrode fabricating process of a pad portion.
In order to achieve these and other objects of the invention, a plasma display panel according to an embodiment of the present invention includes driving waveform supplying means for applying a driving waveform to electrodes provided at the effective display part; a plurality of pads for applying the driving waveform inputted from the driving waveform supplying means to the electrodes, said pads having a different length depending on their location; and connecting means provided between the pads and the electrodes to electrically connect the pads to the electrodes.